Consider the following QML code:

import QtQuick

Item {
    function foo(bar: bool) : doesntexist {
    }
} 

Running qmllint on it produces

Warning: l.qml:4:21: "doesntexist" was not found for the return type of method "foo". [unresolved-type]

    function foo(bar: bool) : doesntexist {

                    ^^^^^^

It is correct that the doesntexist type does not exist, however the bar: bool parameter annotation is highlighted instead of the return type where the actual error is. This can also be seen in qmlls

qtdeclarative commit 41a97f06981144ef80a3faf8925753f15c0ff3c6